1. Field of Technology
The present invention relates to a playback apparatus for playback of a recording medium having recorded thereon audio data and also still picture data expressing a plurality of still pictures, together with information specifying timings during playing of the audio data at which respective ones of the still pictures are to be displayed by the playback apparatus.
In particular, the invention relates to such a playback apparatus which is applicable to a recording medium consisting of an optical readout type of compact disk (CD) having still picture and audio data recorded thereon as a digital bit stream, with the data being recorded as a plurality of data portions referred to as tracks which are managed as separate units. It should be noted that the term xe2x80x9ctrackxe2x80x9d is used in the following description and in the appended claims only with the significance defined above.
2. Description of Prior Art
With a prior art type compact disk (generally referred to in the following as a CD) which is an optical recording disk that is utilized only for recording music, each of respective musical items that are recorded on the CD are managed in units of tracks, i.e., with the recorded audio data portion which expresses one musical item being recorded as one track, and with successive tracks being recorded sequentially in a recording region of the disk. In addition, such a CD has recorded thereon track control information (TC) which indicates the respective leading addresses, final addresses and playing durations, etc. for each of the tracks which are recorded on the disk, where the term xe2x80x9caddressxe2x80x9d is used here to signify a position of recorded data on a CD, expressed for example as a sector number. The track control information is used by the playback apparatus for selecting a specific track to be played, in response to a user input command which specifies playing of that particular track.
In recent years it has become possible to record a substantial amount of digital data, e.g., 600 MB, on a CD having a diameter of 12 cm, of the type which has in the past been generally used for recording music. For that reason, such CDs have come into use as data storage devices of read-only type, referred to as CD-ROMs, for recording various types of digital data. In addition, CD-ROMs have come into use for recording music information together with other types of information, for example video CDs which have recorded thereon audio data and also still picture or video data, with resultant pictures being displayed at predetermined times during playback of the audio data. Such video CDs are applied to uses such as digital video karaoke, music videos, animated cartoons, language teaching materials, teaching materials for infants, etc., so that the applications of CDs have expanded into a wide range. In addition, DVDs (digital video disks), which are a type of video CD having very large storage capacity, have now been put into practical use.
In the case of video CDs which have a file structure that is based on the ISO 9660 standard, the disk has a lead-in region at the inner periphery of the disk, a lead-out region at the outer periphery of the disk, and the tracks are successively numbered from 1 to 99.
Data expressing a TOC (table of contents) is recorded in the lead-in region. The TOC contains information specifying various information that is necessary for playing selected tracks such as the starting addresses (i.e., the starting positions on the disk of each of the regions in which the respective tracks are recorded on the disk) etc., with the various tracks being assigned successive numbers. Track No. 1 (video CD track) has recorded therein various files for use in disk management, playback control data, still picture data, and an application program which is required for activating the operation of a CD-I player. Video/audio bit streams which have been subjected to MPEG 1 compression are recorded in each of the tracks numbered from 2 to 99. Information indicating termination of the program is recorded in the lead-out region.
With the widening of the range of applications of CDs which has occurred as described above, a type of playback apparatus is now in use for playing video CDs which have audio data and video data recorded thereon, with the audio data formed into a plurality of tracks and the video data expressing a plurality of still pictures which start to be displayed at respectively predetermined time points during playback of the audio tracks. With such a video CD, the respective sets of data expressing the still pictures are recorded within the audio data tracks, i.e. each track can contain one or more sets of still picture data together with the audio data. Approximately 10 to 20 still pictures can be recorded on each track, and respectively displayed at predetermined time points during playing of a track.
FIG. 5 is a diagram for use in describing the general arrangement of recorded data on such a prior art type of CD in which both audio data and still picture data can be recorded in each track, with the audio data and the sets of still picture data being recorded in succession within a track. Track control information sets TC1 to TC3 are recorded in the TOC region at the innermost periphery of the disk, and the data of tracks 1 to 3 are successively recorded following the track control information sets TC1 to TC3, i.e. in the recording region which succeeds that in which the track control data sets are recorded.
In FIG. 5, the track control information TC1 consists of control information formed of the leading address and final address of the data recorded on track 1, the playing duration of that track, etc. Similarly, the sets of track control information TC2 and TC3 respectively constitute control information formed of the leading address and final address on the disk, and the playing duration, for tracks 2 and 3. Each of the sets of data recorded on tracks 1 to 3 is formed as a plurality of still picture/audio data blocks, with the internal configuration of such a block being shown in FIG. 5 for the case of track 1. Such a still picture/audio data block contains all of the data expressing one still picture, with the data being divided into a plurality of segments as shown, so that the block is formed of a plurality of segments of the data expressing that still picture, alternating with portions of the audio data of that block. During playing of the track containing such a block, the successive still picture data segments are sequentially read out from the recording medium and are stored in a memory. When all of these data segments have been stored, they are combined into a single data set, which is then decoded to generate a video signal expressing the corresponding still picture, which can thereby be displayed.
It can thus be understood that with such a method, by making each of the plurality of still picture data segments within each still picture/audio data block sufficiently short, periods of discontinuity in audio playback which result from reading out of still picture data from the recording medium can be made correspondingly short, so that effectively continuous playback of the audio data of a track can be achieved.
However with a prior art type of optical recording disk having the data recording arrangement described above, the timings at which the respective still pictures expressed by the sets of still picture data recorded in a track are displayed, during playing of the audio data of that track, are fixedly determined by the arrangement of data on the disk, i.e., by the respectively positions at which the sets of still picture data are located within each track. This can result in delays occurring in playing of the audio data, due to time required to execute disk control operations relating to the still picture data. Furthermore when the recorded data are arranged on the disk in such a way, then in the production of such optical recording disks, if it should become necessary to rearrange or delete any of the still picture data after the data arrangement on the disk has been completed, complex data processing operations must be repetitively performed.
A further disadvantage is that, if the same still picture is to be displayed a number of times within the playing of one track or is to be displayed in each of a plurality of tracks, then the data of that still picture must be recorded a corresponding number of times in accordance with the respective timings at which the still picture is to be displayed. This is a significant disadvantage, since such recording of multiple copies of each of one or more still pictures on an optical recording disk may substantially reduce the proportion of the overall capacity on the disk that is available for recording of audio data.
It is an objective of the present invention to overcome the problems of the prior art described above by providing a playback apparatus and a corresponding recording medium whereby the playback apparatus can display any still picture that is expressed by a still picture data set which is recorded on the recording medium, at each of a plurality of timings which are specified by information recorded on the recording medium, during playback of audio data that are recorded on the recording medium, without the need to record such a still picture data set a corresponding plurality of times.
More specifically, a playback apparatus according to the present invention is adapted to execute playback of a recording medium having an audio data recording region in which are recorded all of respective audio data sets constituting a plurality of tracks, a still picture data recording region in which are recorded data expressing one or more groups of still pictures, with each group including all of a set of still pictures that are to be displayed during playback of the audio data of a track, and a track control information recording region having recorded therein respectively separate sets of track control information for each of the tracks. Each such set of track control information for a track includes, in addition to information for specifying the respective positions at which the tracks are recorded on the recording medium and the playing durations of the tracks:
(a) information which identifies a specific one of the aforementioned groups (i.e., a still picture group containing all of the still pictures that are to be displayed during playing of the audio data of that track) and specifies the range (i.e., initial address and final address) of the region in which the data of that group of still pictures are recorded on the recording medium,
(b) information for individually identifying those still pictures (within the specified group), which are to be displayed during playing of that track, and respective positions of the data sets expressing these still pictures, within the data expressing the specified group, and
(c) information for specifying the respective time points at which displaying of each of the identified still pictures is to begin, with reference to the commencement of playback of the audio data of that track.
When a track of the recording medium is selected to be played (i.e., by an input command supplied to the playback apparatus by a user), the video data of the still picture group that is specified as corresponding to the selected track by the corresponding track control information set are read out from the recording medium and stored in a memory. Readout of the audio data of the selected track then begins, and the sets of video data expressing respective ones of the still pictures that are to be displayed during playback of that track are thereafter read out from the memory at timings which are specified by the track control information.
As a result, if it should become necessary during the production of such a recording medium to alter the arrangement of still picture data on the recording medium or to delete any of the still picture data, after layout of data on the recording medium has been completed, such rearrangement or deletion of data can easily be performed without the need to execute complex data processing operations.
In addition, if it is required to display a still picture a plurality of times during playing of a specific track (i.e., a still picture which is included in the group of still pictures predetermined as corresponding to that track) then such operation can be specified in the track control information of that track, without the need to record multiple copies of the data of such a still picture on the recording medium.
Similarly, if it is required to display each of a specific set of one or more still pictures during playback of the audio data of each of a plurality of tracks, then this can be achieved by recording the data of a single still picture group which contains all of that set of still pictures, and which is specified as corresponding to each of that plurality of tracks (i.e., which is identified within the respective track control information sets of that plurality of tracks). Here again, recording of multiple copies of the data of such still pictures on the recording medium is made unnecessary.
Furthermore, after playback of a selected track has been completed, the still picture data of the still picture group corresponding to that track are left stored in the still picture data memory during any subsequent playing of other tracks of the recording medium. When playback of a selected track is to be executed, the still picture group which is identifed in the track control information set of the selected track is first compared with the contents of the still picture data memory, to find if the data of that still picture group have already been stored in the still picture data memory. If so, then such data are read out from the memory and utilized, without requiring any operation for storing such still picture data in the memory to be executed at that time. This serves to reduce any occurrence of discontinuity in the output audio signal which is obtained from playback of successively selected tracks.